Method and apparatus for blow molding

ABSTRACT

A method and apparatus for blow molding an article wherein a parison is positioned between three or more mold closures, the mold closures are advanced along a first axis and an axis generally transverse to the first axis, a gas is injected within the interior of the parison to form a molded article, the mold closures are retracted along their respective axes, and the molded article is removed.

FIELD OF THE INVENTION

This invention relates generally to molding processes and apparatusesand more particularly to plastic blow molding processes and apparatuses.

BACKGROUND OF THE INVENTION

Blow molding is a well known method for producing a variety of plasticproducts, particularly hollow vessels including fuel tanks, containers,and the like. As depicted in FIG. 1, a blow molding process andapparatus M typically involves spreading portions of a heated pre-formedplastic article A between two spreader pins P. As shown, blow moldingprocesses almost universally involve molding the hot pre-formed articleA between two mold halves Hl and Hr, which open away from one anotherand close together along a single axis X.

One variation on this concept is disclosed in U.S. Pat. No. 5,198,174 toNakagawa et al. Nakagawa et al is directed toward the problemsassociated with forming a radially extended flange portion at one end ofa hollow plastic product, such as a flanged pipe. Nakagawa et al.asserts that it is nearly impossible to simultaneously and integrallyblow mold a tubular portion with a hollow head or a radially extendingflange portion at one end of the tubular portion due to unacceptablethinning of the material at the corners of the flange portion.Therefore, Nakagawa et al instead teach a method of blow molding thetubular portion and then injection molding a solid radially extendingflange portion on the tubular portion. Nakagawa et al disclose a blowmold having a pair of mold closures or mold halves that close toward oneanother along an axis. Each of the mold halves includes a recess and amating surface. When the mold halves come toward one another, theirrespective mating surfaces engage one another to close the mold. Inother words, the closed mold is established by the closure of the moldhalves together such that the mating surfaces engage. A first moldcavity is defined not only by the recesses of the mold halves, but alsoby movable mold segments that are mounted within the mold halves andthat are moved to an advanced position within the mold halves. The firstmold cavity is provided to blow mold the tubular portion of the hollowarticle. A second mold cavity is defined by the movable mold segmentswhen they are moved to a retracted position within the mold halves. Thesecond mold cavity is provided to injection mold the solid flangeportion of the hollow article.

Another variation is disclosed in U.S. patent application Publication2002/0171161 to Belcher. Belcher identifies several problems withcombining blow molding and injection molding operations to form a singlehollow article, such as a bottle with a handle. Belcher teaches a methodof blow molding a bottle and thereafter pinching side walls of the blownbottle so as to bond adjacent interior wall surfaces together to formthe handle. Belcher discloses a blow mold having two mold closures; afront half section and a rear half section that define the front andrear of the bottle and traverse toward one another along an axis. Bothhalf sections have mating surfaces that engage one another to close themold and define a mold cavity, wherein the bottle is expanded or blown.A movable mold segment is mounted within each of the half sections tomove along an axis that is parallel to the closure axis. The movablemold segments are linearly opposed and move toward one another from aretracted position to an advanced position to pinch opposed portions ofthe blown bottle together to form an integral handle.

Thus, the Nakagawa et al and Belcher references both teach theconventional method of closing a mold by bringing two mold closures ormold halves together. Unfortunately, however, the use of two mold halvesto close a blow mold has some drawbacks. Referring again to FIG. 1, moldhalves Hl and Hr engage one another along mating engagement surfaces Sland Sr in a closed position as shown. During a blowing step, relativelylarge portions of the pre-formed article A tend to get pinched betweenthe mating engagement surfaces Sl and Sr of the mold halves Hl and Hr,which is an undesirable condition. As shown in FIG. 2, this pinchingphenomenon creates a heavy parting line L in a finished blow moldedarticle B. Pinching of pre-formed material and resulting heavy partinglines are especially problematic when blow molding a multi-layerarticle, such as that shown, which includes a relatively thin andfragile inner membrane I. Due to the pinching of the pre-formed articlebetween the mold halves, such membranes can become ruptured in variousplaces along the parting line, as shown by rupture R. Ruptured membranesare undesirable, especially when the purpose of such membranes is toprevent vapor permeation through the wall of the finished blow moldedarticle. Specifically, hydrocarbon vapors can escape to atmospherethrough the walls of a fuel tank through such ruptured membranes.

Another problem associated with conventional blow molding processes andapparatuses involves unnecessarily high stretch ratios of pre-formedarticles. In other words, conventional blow molding typically involvesusing parisons or pre-formed articles, wherein portions thereof must beblown or expanded to two to three times their original size in order toachieve the final dimensions of the finished blow molded article.Accordingly, some portions of the pre-formed article will experience ahigh stretch ratio, thereby resulting in significant thinning of thewall thickness of those portions, as discussed in the Nakagawa et al.reference. In contrast, other portions of the pre-formed article willexperience a low-stretch ratio, thereby resulting in relatively littlethinning. This significant difference in stretch ratios over theentirety of the pre-formed article tends to result in a finishedblow-molded component with a wall thickness distribution that issubstantially non-uniform.

SUMMARY OF THE INVENTION

A method of blow molding an article which generally includes the stepsof positioning a parison between three or more mold closures, advancingthe mold closures along two or more axes to close the mold closuresaround the parison, and blow molding the parison to produce the article.More specifically, the method of making the article may include thesteps of: positioning a parison between multiple mold closures;advancing one or more of the multiple mold closures along a first axisand advancing one or more other of the multiple mold closures alonganother axis, which is generally transverse to the first axis; injectinga gas within the interior of the parison; retracting the mold closuresalong their respective axes; and removing a molded article formed fromthe parison. Articles are also produced by the processes describedabove.

An apparatus for blow molding an article from a parison is alsoprovided. The apparatus includes first and second opposed mold closuresthat are retractable between open and closed positions along an axis.The apparatus further includes one or more other mold closures that aretranslatably mounted to the first and second opposed mold closures andare retractable between open and closed positions along another axis.

Objects, features, and advantages of this invention include providing anapparatus and method for producing an article that improves the surfacequality and internal integrity of a blow molded article, reduces thehydrocarbon permeability of a blow molded fuel tank, reduces the stretchratio of a blow molding operation, enables blow molding of flangeportions, enables use of a relatively larger parison than beforepossible, eliminates the need to use pinch plates and pre-blowing,better facilitates the blow molding of a fuel tank around a carrier toproduce a “Ship-In-a-Bottle” article that is of relatively simpledesign, economical manufacture and assembly, and has a long servicelife.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of this invention willbe apparent from the following detailed description of the preferredembodiments and best mode, appended claims, and accompanying drawings inwhich:

FIG. 1 is a cross-sectional view of a blow molding apparatus inaccordance with the prior art;

FIG. 2 is a partial cross-sectional view of a prior art blow moldedcomponent manufactured using the prior art apparatus of FIG. 1;

FIG. 3A is a partial cross-sectional view of a blow molding apparatus inan open or retracted position, according to an embodiment of the presentinvention;

FIG. 3B is a partial cross-sectional view of the blow molding apparatusof FIG. 3A along lines 3B-3B, illustrating spreader pins engaging alower portion of a parison;

FIG. 3C is a partial cross-sectional view of the blow molding apparatusof FIG. 3A, illustrating the spreader pins fully extended and a blow pinmechanism and a carrier extending up into the parison;

FIG. 4 is a cross-sectional view of the blow molding apparatus of FIG.3A in a closed or advanced position with the parison fully spread by thespreader pins;

FIG. 5A is a partial cross-sectional view of the blow molding apparatusof FIG. 3A, illustrating gas being injected through the blow pin tofully expand the parison;

FIG. 5B is a cross-sectional view of the blow molding apparatus of FIG.3A, illustrating the parison being fully blown into final position; and

FIG. 6 is a partial cross-sectional view of a blow molded componentproduced by the apparatus of the present invention and/or in accordancewith the method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring in detail to the drawings, FIG. 3A illustrates a blow moldingapparatus 10 of the invention, which is constructed for use with a blowmolding machine 12. The blow molding apparatus 10 is depicted in crosssection, looking downward along a Z axis with an X axis extending leftto right and a Y axis extending rear to front. As defined herein, X, Y,and Z are orthogonal axes and each axis represents a relative direction,rather than a specific line along that direction. Moreover, the termsleft, right, front, and rear are used as an expedient for more clearlyexplaining the present invention, and are not to be interpreted aslimiting the present invention to the orientations described herein. Theblow molding apparatus 10 includes left and right base frames 14 and 16that are attached to left and right movable platens or mold closers 18and 20 of the blow molding machine 12. The base frames 14 and 16 may beconstructed in an open space frame configuration as is well known in theart, such as from a weldment or a casting, such that hydraulic lines,coolant lines, and the like can be routed therethrough. Likewise, themold closers 18 and 20 are well-known in the art and are typicallycomponent parts of the blow molding machine 12 that are activatedhydraulically.

Unlike prior art blow molding apparatuses that only include two opposedmovable mold halves, the blow molding apparatus 10 of the presentinvention includes a plurality of movable mold closures or segments,which are shown in FIG. 3A in a retracted or open position. Theplurality of movable mold segments includes a left mold segment 22mounted on the left base frame 14 and a right mold segment 24 mounted onthe right base frame 16. Accordingly, the mold closers 18 and 20 arecapable of traversing the left and right mold segments 22 and 24 betweenopen and closed positions along the X axis. Rear and front left moldsegments 26 and 30 are slidably mounted to the left segment 22, and rearand front right mold segments 28 and 32 are slidably mounted to theright segment 24. Thus, the rear and front mold segments 26, 28 and 30,32 are slidable between open and closed positions along the Y axis. Asshown, the rear and front mold segments 26, 28 and 30, 32 moveperpendicularly transverse to the X axis motion of the left and rightmold segments 22, 24. However, the mold segments 22, 24, 26, 28, 30, 32may move in any generally oblique or transverse directions with respectto one another. Each of the mold segments 22, 24, 26, 28, 30, 32 ispreferably jacketed with cooling passages therethrough as is well knownin the art.

The rear and front mold segments 26, 28 and 30, 32 need not be mountedto their respective left and right mold segments 22 and 24, but insteadcould be separately mounted to the blow molding machine 12, such as byrear and front mold closers (not shown), similar to the left and rightmold closers 18 and 20. While this specific mounting configuration ofthe mold segments and closures of the present invention is particularlycost effective, it is contemplated that other, more complex moldsegments and closure arrangements could be provided and still fall wellwithin the scope of the present invention. For example, three or moremold segments could be arranged radially with respect to a commoncenter, wherein the mold segments advance radially inwardly toward thecommon center.

In any case, each of the left and right mold segments 22 and 24 includesmold surfaces 22 a and 24 a, which partially define a mold cavity 34.The mold cavity 34 is further defined by mold surfaces 26 a, 28 a, 30 a,and 32 a of respective mold segments 26, 28, 30, 32. Likewise, all ofthe mold segments 22, 24, 26, 28, 30, 32 collectively define a mold ofthe present invention. The rear and front mold segments 26, 28, 30 and32 also include abutment surfaces 26 b, 28 b, 30 b, and 32 b; drivensurfaces 26 c, 28 c, 30 c, and 32 c; and sliding surfaces 26 d, 28 d, 30d, and 32 d. Likewise, left and right mold segments 22 and 24 includesliding surfaces 22 r, 22 f, and 24 r, 24 f for respective slidingengagement with sliding surfaces 26 d, 30 d, and 28 d, 32 d.

The rear mold segments 26 and 28, and the front mold segments 30 and 32,are slidably mounted to respective portions of the left and right moldsegments 22 and 24 using an interlocking guide rail arrangement.Interlocking guide rail arrangements are well known in the art ofmachine and tool design. In any case, guide rail support blocks 36 areT-jointed and fastened to respective portions of the left and right moldsegments 22 and 24. The guide rail support blocks 36 are provided forsupporting STAR brand guide rails 38 thereon. The guide rails 38 aremounted to and fastened atop the support blocks 36 and the respectivesliding surfaces 22 r, 22 f, 24 r, 24 f of the left and right moldsegments 22 and 24. The guide rails 38 interengage with STAR brandstandard runner blocks 40, which are mounted to and fastened withinchannels (not shown), which are milled into respective sliding surfacesof the mold segments. Accordingly, the rear and front mold segments 26,28, 30, 32 are slidable fore and aft along the Y axis.

To slide the rear and front mold segments 26, 28, 30, 32 along the Yaxis, HEB brand hydraulic cylinders 44 are mounted to the drivensurfaces 26 c, 28 c, 30 c, and 32 c of the rear and front mold segments26, 28, 30, 32, preferably by a clevis arrangement (not shown). Thehydraulic cylinders 44 are preferably of a self-locking type and aresupported by weldment brackets 46, which are mounted and fastened to theleft and right mold segments 22 and 24 and to the left and right baseframes 14 and 16 as shown. Accordingly, the X axis motion of each of theleft and right mold segments 22 and 24 is independently controllable,and the Y axis motion of each of the rear and front mold segments 26,28, 30, 32 is independently controllable.

Shown in FIG. 3A, positioned just below the open mold cavity 34, is afour way spreader device defined partially by four vertically disposedspreader pins 48. Two-way spreader devices are well known in the art ofblow molding machine design. The four-way spreader, however, providesfour spreader pins, instead of two, that are movable radially outwardlywith respect to one another. Accordingly, the four-way spreader providesmore of a 360 degree contact with an article, compared with the 180degree contact of two-way spreaders of the prior art.

Positioned centrally of and just below the four-way spreader is a blowpin device 50. Blow pin devices are generally known in the art forcommunicating a gas under pressure with the interior of an article to beblow molded within the mold cavity of a blow mold. With the presentinvention, however, the blow pin device 50 includes a socket 52, or agripper device, for releasably holding a carrier 54 thereon.

The carrier 54 is an assembly that includes a main structural member anda plurality of components thereon, wherein the assembly is ultimatelyreceived within a final blow molded article. As defined herein, however,the carrier 54 may be any type of separate component or sub-assemblythat is suitable for insertion within a vessel or other blow moldedarticle. The carrier 54 may also function as a baffle or divider plate,which divides the volume of a finished, blow-molded, vessel into smallerportions and eliminates or reduces surging or splashing of large amountsof liquid within the finished vessel. Advantageously, the carrier 54 isat least locally connected, and preferably bonded or welded, to theinside of the finished vessel. To this end, the carrier 54 may have aplurality of feet or connecting elements (not shown) spaced along itsedges, which consist of a plastic material that is weldable or bondableto the inside of the finished vessel. The remainder of the carrier 54may therefore consist of a plastic material, which is not weldable orbondable to the material of the tank, or it may consist of a metal. Thecarrier 54 is similar to that disclosed in U.S. patent applicationPublication 2001/0013516, which is assigned to the assignee hereof andis incorporated by reference herein.

Finally, a parison 56 is shown in cross-section and encircles the fourway spreader. The parison 56 is preferably a molten, plastic, tubularpreformed article. The parison 56 preferably comprises a plurality oflayers of different thermoplastic polymer materials that aresimultaneously extruded. For example, in a six layer co-extrusion of theparison 56 for making a vehicle fuel tank, the parison 56 has inner andouter structural layers of polyethylene (such as HDPE), and may have alayer of so-called “re-grind” or recycled scrap material between theouter layers, and a fuel vapor barrier layer (of ethylene vinyl alcoholor other polymer resistant to fuel vapor permeation) that is sandwichedbetween two adhesive layers which connect the vapor barrier layer to thestructural polymeric layers of re-grind and/or virgin HDPE.

FIG. 3B illustrates a cross-sectional view of the blow molding apparatus10 of FIG. 3A, taken along line 3B-3B. The open mold cavity 34 ispartially defined by the mold surfaces 22 a, 24 a, 26 a, 28 a of thevarious mold segments 22, 24, 26, 28. The blow pin device 50 and carrier54 are shown in a fully lowered or retracted position.

In a method according to one embodiment of the present invention, anextruder 58 produces the parison 56. The extruder 58 is preferably aco-extrusion device, which is well known in the art. The extruder 58essentially processes an input of plastic pellets to form an output of aco-extruded tubular preform of hot plastic, otherwise known as theparison 56. The parison 56 may be gravity fed directly to the open moldcavity 34 between or amongst the various mold segments 22, 24, 26, 28,30, 32. Alternatively, the parison 56 may be gripped by a transfermechanism (not shown), torn from the extruder 58, and transported intothe open mold cavity 34 for blow molding into a finished article orvessel, such as a fuel tank. In any case, the parison 56 is lowered to apoint where a lower end 60 of the parison 56 encircles the spreader pins48, which are in a closed or retracted position.

As shown in FIG. 3C, the spreader pins 48 are positioned within thelower end 60 of the parison 56. It is contemplated that the spreaderpins 48 can extend vertically upward deep into the interior of theparison if desired. In any case, the spreader pins 48 are movedlaterally apart, or radially outwardly. Accordingly, the spreader pins48 spread out the lower end 60 of the parison 56 to better distributethe parison material within the mold and to further open at least thelower portion of the parison 56.

Preferably after the four-way spreader has spread or opened the parison56, the blow pin device 50 and carrier 54 are extended upwardly into theparison 56 to an advanced position within the mold. The carrier 54 maybe loaded into the socket 52 of the blow pin device 50 manually orautomatically, such as by a robot (not shown). Blow pin devices 50 andthe means for advancing blow pin devices are generally well known in theart of blow molding. The present invention, however, contemplates theuse of rodless pneumatic cylinders, or HEB brand pneumatic hollow rodcylinders, in order to provide the blow pin advancing motion. The hotparison 56 is somewhat molten, flexible and sticky, so care must betaken to maintain the parison 56 separate or spaced from the carrier 54.Ordinarily, a supply of pressurized air may be provided into the parison56 to maintain it open and prevent it from collapsing or otherwiseengaging the carrier 54 prior to closing the mold. However, such apre-blowing step is usually not necessary when using the fourequidistantly spaced spreader pins 48 of the four-way spreader device,which sufficiently keeps the parison 56 opened to prevent contact withthe carrier 54.

Preferably, when the blow pin device 50 and carrier 54 are extended tothe fully advanced position, the mold closes. Accordingly, FIG. 4illustrates the blow molding apparatus 10 in an advanced or completelyclosed position, wherein the left and right mold segments 22 and 24, andthe upper and lower mold segments 26, 28, 30, 32 have been advancedinwardly toward the now spread out parison 56. Preferably, the left andright mold segments 22 and 24 are advanced to a closed position first,and then the rear and front mold segments 26, 28, 30, 32 are advanced totheir closed positions although they could be closed in the reverseorder. Alternatively, all of the mold segments 22, 24, 26, 28, 30, 32may be advanced simultaneously so as to provide simultaneouscircumferential closure of the mold around the parison 56.

The mold is closed when the abutment surfaces 26 b and 28 b of the rearmold segments 26 and 28 abut one another and when abutment surfaces 30 band 32 b of the front mold segments 30 and 32 abut one another. Closureof the mold traps the parison 56 and closes its ends with the blow pindevice 50 extending into the parison 56 within the mold cavity 34.Preferably, the left and right mold segments 22 and 24 include a sealingaperture (not shown) for engaging and sealing around a portion of theblow pin device 50. As is well known in the art of blow molding, aportion of the extruded parison 56 is severed between the top of themold and the bottom of the extruder and another portion is severed belowthe bottom of the mold, such that the parison 56 remains intact withinthe mold and is sealed by the mold.

Desirably, as the mold is closed, the parison 56 engages feet (notshown) of the carrier 54 to limit or prevent relative movement betweenthe carrier 54 and the parison 56. To adhere to the parison 56, the feetare preferably a polymeric material directly bondable to the innermostlayer of the parison 18, such as HDPE or re-grind material. Theremainder of the carrier 54 can be made out of any material suitable foruse in the liquid fuel to be stored in the tank, including withoutlimitation, metals and polymers such as HDPE or re-grind material.

As shown in FIG. 5A, with the parison 56 positioned within the closedmold, pressurized air may be provided through apertures 62 of the blowpin device 50 to expand the parison 56 into engagement with the variousmold surfaces in order to form the final shape of the finished blowmolded article. The pressurized air may be at a pressure of about 10 barand, to facilitate cooling the parison 56 (which may be extruded atabout 250 degrees Celsius), the mold may be chilled to about 10 degreesCelsius using standard cooling passages formed within the various moldsegments.

Sixth, FIG. 5B illustrates the parison fully blown and shaped into afinal molded article 64 within the closed mold. After the blow moldedarticle 64 has cooled sufficiently to retain its shape, the supply ofpressurized air is turned off, the blow pin device 50 withdrawn, themold opened, and the blow molded article 64 removed.

FIG. 6 illustrates a partial cross-sectional view through the wall ofthe molded article 64. The molded article 64 is a multi-layer componentas described above and preferably includes six layers. For simplicity,the wall is shown as including a sensitive inner membrane 66 that issandwiched between an outer layer 68 and an inner layer 70. Forexemplary purposes, and referring to FIG. 6 and FIG. 3A, the partingline 72 results from the interface of the sliding surfaces 22 r and 26 dof the left mold segment 22 and rear left mold segment 26. Similarly,parting line 74 results from the interface of the abutment surfaces 26 band 28 b of the rear mold segments 26 and 28. Likewise, parting line 76results from the interface of the sliding surfaces 28 d and 24 r of therear right mold segment 28 and the right mold segment 24. Unlike priorart molding apparatuses and methods, however, the present invention doesnot result in large parting lines that yield ruptures in the innermembrane 66. Accordingly, the present invention enables fuel tanks to beblow molded without compromising the structural integrity of the layersthereof. In other words, the present invention yields fuel tanks inwhich the barrier layer is imperforate so that no hydrocarbons canescape through any breaches or voids in the fuel tank wall.

With this invention, it is now possible to integrally blow mold a flangeportion on a relatively narrow and generally tubular or cylindricalhollow vessel. The sliding mold segments of the present invention arecapable of opening or retracting along multiple axes, which facilitatesuse of a relatively larger parison than before possible. In turn, usinga larger parison translates into a reduced stretch ratio when blowmolding the parison. This is because the larger parison can be sized toapproximate the size of the interior of a narrower portion of the moldcavity compared to a relatively larger flange portion of the moldcavity. The difference in diameter between the portions of the moldcavity may be about two to one. In accordance with the presentinvention, a portion of the larger parison is expanded very little orjust enough to engage the narrower portion of the mold cavity, andanother portion of the larger parison is expanded in accordance with astandard, acceptable stretch ratio to engage the larger flange portionof the mold cavity. In other words, and as an example, the largerparison may undergo a stretch ratio of about one in a narrower portionof the mold cavity and a stretch ratio of about two to one in the largerflange portion of the mold cavity. With conventional two-piece molds andusing conventional blow molding methods, such a configuration wouldrequire much larger differences in stretch ratios between a relativelynarrow portion of a mold cavity and a relatively larger flange portionof a mold cavity. For example, a conventional approach would requireusing a relatively smaller parison that would undergo a stretch ratio ofabout one to two in the narrower portion of the mold and a stretch ratioof about three to two in the larger flange portion of the mold. Thus,the present invention provides a significant improvement in the art ofblow molding that yields lower stretch ratios and more uniform wallthickness of blow molded components, and that avoids excessive flash andrupturing of sensitive inner membranes.

Using movable mold segments that traverse in a plurality of generallytransverse axes, permits using a larger parison, which in turn,accommodates use of a “Ship-in-a-Bottle” fuel tank and carrier design. Alarger parison has a larger internal diameter, which facilitatesinserting larger carriers therein during a blow molding process. In thepast, it has sometimes been required to manufacture a fuel tank from twohalf-shells in order to accommodate assembly of a carrier or largecomponents within the fuel tank. Such fuel tank manufacturing techniquestend to be more difficult and costly than fuel tank blow moldingtechniques and tend to have unacceptably high hydrocarbon permeationlosses. Thus, the present invention provides a method of blow moldingfuel tanks that is less expensive than prior art methods and thatresults in a fuel tank with comparably higher structural integrity andsignificantly lower hydrocarbon permeation losses.

While the forms of the invention herein disclosed constitute a presentlypreferred embodiment, many others are possible. For instance, the moldsegments may be independently arranged and not mounted to one another,and the mold segments may move in oblique axes other than theperpendicularly oriented X and Y axes. It is not intended herein tomention all the possible equivalent forms or ramification of theinvention. It is understood that terms used herein are merelydescriptive, rather than limiting, and that various changes may be madewithout departing from the spirit and scope of the invention as definedby the following claims.

1. A method of blow molding comprising the steps of: positioning aparison between at least three mold closures; and advancing said atleast three mold closures along at least two generally transverse axesto close said mold closures around said parison.
 2. The method of claim1 further comprising the step of providing a carrier assembly within aninterior of said parison.
 3. The method of claim 2 further comprisingthe steps of: mounting said carrier assembly to a blow pin; extendingsaid blow pin with said carrier assembly mounted thereto into theinterior of said parison.
 4. The method of claim 3 further comprisingthe step of injecting a pressurized gas within the interior of saidparison to expand said parison outwardly within said mold closures. 5.The method of claim 1 wherein said advancing step comprises the stepsof: advancing substantially opposed mold segments toward one anotheralong a first axis; and advancing other substantially opposed moldsegments toward one another along a second axis.
 6. The method of claim5 wherein said step of advancing other substantially opposed moldsegments comprises the steps of: slidably mounting a first pair of moldsegments to one of said substantially opposed mold segments; andslidably mounting a second pair of mold segments to another of saidsubstantially opposed mold segments.
 7. An article produced by themethod as claimed in claim
 1. 8. A method of blow molding comprising thesteps of: positioning a parison between a plurality of mold closures;advancing at least one of said plurality of mold closures along a firstaxis and at least one other of said plurality of mold closures along atleast one other axis that is generally transverse to said first axis;injecting a pressurized gas within the interior of said parison;retracting said at least one of said plurality of mold closures alongsaid first axis and said at least one other of said plurality of moldclosures along said at least one other axis; and removing a moldedarticle formed from said parison.
 9. The method of claim 8 furthercomprising the step of providing a carrier assembly within an interiorof said parison.
 10. The method of claim 9 further comprising the stepsof: mounting said carrier assembly to a blow pin; extending said blowpin with said carrier assembly mounted thereto into the interior of saidparison.
 11. The method of claim 8 wherein said advancing step comprisesthe steps of: advancing a pair of substantially opposed mold segmentstoward one another along said first axis; and advancing at least oneother pair of substantially opposed mold segments toward one anotheralong said at least one other axis.
 12. The method of claim 11 whereinsaid step of advancing at least one other pair of substantially opposedmold segments comprises the steps of: slidably mounting a first pair ofmold segments to one of said substantially opposed mold segments; andslidably mounting a second pair of mold segments to another of saidsubstantially opposed mold segments.
 13. An article produced by themethod as claimed in claim
 8. 14. A method of blow molding comprisingthe steps of: positioning a parison between at least three moldclosures; advancing at least one of said at least three mold closuresalong a first axis, and at least one other of said at least three moldclosures along a second axis that is substantially perpendicular to saidfirst axis, until at least one mating surface of said at least threemold closures mates with at least one other mating surface of said atleast three mold closures; injecting a pressurized gas into the interiorof said parison; retracting said at least one of said plurality of moldclosures along said first axis and said at least one other of saidplurality of mold closures along said second axis; and removing a moldedarticle formed from said parison.
 15. The method of claim 14 furthercomprising the step of providing a carrier assembly within an interiorof said parison.
 16. The method of claim 15 further comprising the stepsof: mounting said carrier assembly to a blow pin; extending said blowpin with said carrier assembly mounted thereto into the interior of saidparison.
 17. The method of claim 14 wherein said advancing stepcomprises the steps of: advancing a left side mold segment toward aright side mold segment along a first axis; advancing a rear left moldsegment toward a front left mold segment another along a second axis;and advancing a rear right mold segment toward a front right moldsegment along said second axis.
 18. The method of claim 17 wherein saidadvancing steps further comprise the steps of: slidably mounting saidleft rear and left front mold segments to said left side mold segment;and slidably mounting said right rear and right front mold segments tosaid right side mold segment.
 19. A fuel tank produced by the method asclaimed in claim
 14. 20. An apparatus for blow molding a finishedarticle from a preformed parison, said apparatus comprising: first andsecond opposed mold closures, said first and second opposed moldclosures being retractable between open and closed positions along afirst axis; and at least one other mold closure being translatablymounted to at least one of said first and second opposed mold closures,said at least one other mold closure being retractable between open andclosed positions along a second axis which is not parallel to said firstaxis.